Infrared Lattice Vibrations of CdGa2Te4

Infrared reflectivity spectra of CdGa₂Te₄ crystals are measured at room temperature in the wavenumber range from 180 to 600 cm⁻¹ for the polarization directions E ⊥ c and E ‖ [111]. The frequencies of two E modes and two B modes are derived from the spectra. The frequencies of the modes with highest energy compare well with those of the corresponding modes in CuGaTe₂ and AgGaTe₂ which confirms the sphalerite-like nature of these modes.     

One- and two-phonon vibrational spectra of amorphous As- and Sb-chalcogenide systems

One- and two-phonon infrared and Raman spectra of As- and Sb-chalcogenide systems are reported. Both one- and two-phonon Raman and infrared vibrational spectra exhibit two modes type behaviours characteristics to the vibration modes of AsSe₃, AsS₃, and SbSe₃ pyramids. In the infrared spectra, the larger peak shifts are observed for one phonon frequencies than for two phonon frequencies with the change of the composition x, and its suggests rather big local field effects. The two-phonon coupling parameters of the combination modes are estimated.     

Infrared optical properties and crystal structure of Cu2GeS3

Infrared reflectivity and transmission spectra of Cu₂GeS₃ are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. From an analysis of the spectra the parameters of the fundamental infrared active lattice modes and of the two-phonon combination modes are determined. From a comparison of the experimental data with group theoretical predictions for the structure models proposed for Cu₂GeS₃ in the literature it is concluded that Cu₂GeS₃ crystallizes in a monoclinic lattice.     

Two-Phonon Combination Mode Spectra of AgGaS2

Absorption spectra of (001)-oriented AgGaS₂ single crystals are measured in the wavenumber range from 400 to 900 cm⁻¹. The spectra exhibit 12 structures due to two-phonon combination modes which can be all interpreted as sum modes of zone-centre phonons. Possible frequencies for the B₁ and A₂ modes are discussed. The results obtained are compared with second-order Raman spectra of the compound.     

Vibrational and Polariton Spectra of CdGa2S4 and CdAl2S4 Crystals

In this work the vibrational and polariton optical spectra of the CdGa₂S₄ and CdAl₂S₄ crystals grown from vapor phase and by the Bridgman method have been investigated. The light scattering by polaritons excited of various wavelength of Ar⁺ and He‐Ne lasers is studied.     

Infrared lattice vibration study of CuIn5S8

Infrared reflectivity spectra of the spinel compound CuIn₅S₈ are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. It is found that the spectra are dominated by two strong modes with frequencies and oscillator strengths that are practically equal to those of the corresponding modes in the normal spinels of type A^IIIn₂S₄. A very weak additional mode at 357 cm⁻¹ is ascribed to a secondary tetragonal phase previously observed in as-grown CuIn₅S₈ single crystals.     

Infrared Absorption Spectra of CdIn2Te4

Transmittance and reflectance spectra of CdIn₂Te₄ are measured in the wavenumber range from 200 to 4000 cm^–1. In the range from 200 to 400 cm^–1 the spectra are governed by two-phonon combination mode absorptions. In the wavenumber range above 400 cm^–1 absorption coefficients below 1 cm^–1 and a constant reflectivity of about 0.21 are found.     

Infrared reflectivity of ZnIn2Te4

Infrared reflectivity spectra of ZnIn₂Te₄ single crystals are measured at room temperature in the wavenumber range from 170 to 4000 cm⁻¹. The spectra reveal a single vibrational mode the frequency of which compares well with the frequencies of the high-energy infrared active modes in HgIn₂Te₄, CuInTe₂ and AgInTe₂. It is concluded that these modes are sphalerite-like in nature and that they are essentially determined by the properties of the In—Te bond.     

IR and X-Ray Powder Diffraction Studies on Ba2Me(HCOO)6. 4 H2O (Me = Co,Ni, Zn)

It has been established that the double salts Ba₂Me(HCOO)₆. 4 H₂O (Me = Co, Ni, Zn) are isostructural with Ba₂Cu(HCOO)₆. 4 H₂O (trinclinic space group P1 = C¹_i). The infrared spectra of the double salts and their deuterated analogues have been recorded and the internal modes of the formate groups and the water molecules are reported. The analysis of the infrared spectra indicates that some of the internal formate modes (v₃ and v₄) reflect the existence of three crystallographically independent formate ions. The comparatively large frequency separations between the asymmetric and symmetric C–O stretching modes is a criterion for the different C–O bond lengths within each formate groups. The number and the positions of the bands in the high frequency range (4000–2300 cm⁻¹) are evidence for the existence of two inequivalent water molecules. The apearance of four uncoupled O–D modes in the spectra of the isotopically dilute samples shows that the water molecules are asymmetric. The librational modes of the water molecules are discussed as well.     

Effects of Group III Cation Substitution in the Raman Spectra of Some Defective Chalcopyrites

We report on the Raman spectra of CdIn₂Se₄ and ZnIn₂Se₄ obtained in a transparency region. These spectra have a disordered-like appearance at high frequencies. A comparison is made with the Raman and IR spectra of the similar compounds CdGa₂Se₄ and ZnGa₂Se₄. The overall vibrational behaviour is mainly determined by the anion and a correspondence may be observed between the frequencies of some high energy polar modes. A strong non-polar breathing mode is observed at nearly the same frequency in all these compounds. The observed similarities between the spectra are discussed within the frame of the existing simplified models.     

Infrared lattice vibrations of PbGa2S4

Infrared reflectivity spectra of PbGa₂S₄ single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm⁻¹ for the polarization directions E ∥ c and E ∥ b. The frequencies of 13 B_1u modes and 11 B_2u modes are derived from the spectra. The results are compared with previous studies and with lattice vibration data of ternary chalcopyrite and defect-chalcopyrite compounds.     

On the influence of nonstoichiometry on luminescent properties of CdGa2S4 single crystals

Results of a study of photoluminescence and thermoluminescence of cadmium thiogallate single crystals grown from the melt are presented. Effect of nonstoichiometry on the properties of samples is studied. Some assumptions about the nature of centres in CdGa₂S₄ compound are made.     

Infrared Lattice Vibrations of TI3AsS4

Infrared reflectivity spectra of TI₃AsS₄ single crystals are measured at room temperature in the wavenumber range from 30 to 4000 cm⁻¹ for the polarization directions E ‖ c and E ‖ a. An analysis of the spectra with the Kramers-Kronig method reveals 10 infrared active modes for each of the polarization directions. On the basis of theoretical estimates the modes due to TI-S and As–S bond vibrations are identified.     

Infrared optical properties of (CuGe2P3)1−x(6 Ge)x solid solutions

Infrared reflectivity spectra of (CuGe₂P₃)_1−x(6 Ge)_x mixed crystals with compositions in the range x = 0.07–0.33 are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. An analysis of the spectra reveals six vibrational modes. The composition dependence of the mode frequencies and of the free carrier concentration and mobility is given and compared with infrared optical data for CuGe₂P₃.     

Vibrational Properties of LiGaO2 (I). Experimental Results

Infrared reflectivity spectra of LiGaO₂ are measured at room temperature in the wave-number range from 200 to 4000 cm¹ for the polarization directions E ∥ a and E ∥ c. The parameters of 10 B₁ modes and 4 A₁ modes are determined by a dispersion analysis of the spectra. The results obtained are compared with previous Raman scattering measurements.     

Infrared lattice vibrations of CdIn2Se4

Infrared reflectivity spectra of CdIn₂Se₄ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹ for the polarization directions E ⟂ c and E ‖[112]. The spectra reveal two vibrational modes with nearly the same frequencies for both polarization directions. The frequencies of the modes with highest energy compare well with the corresponding mode frequencies in ZnIn₂Se₄, CuInSe₂ and AgInSe₂. It is concluded that these modes are sphalerite-like in nature and that their frequencies are essentially determined by the properties of the In Se bond.     

Optical phonon modes and transmissivity in BaWO4 single crystal

Barium tungstate (BaWO₄) single crystal has been grown using Czochralski technique. It belongs to the scheelite structure, forming the space group I 4₁/a at room temperature and the primitive cell contains two molecular units. The polarized Raman spectra were recorded by a micro‐Raman spectrophotometer system in the backscattering geometry. All the observed Raman modes were assigned. The Raman mode at 924 cm^–1, which belongs to the totally symmetrical A_g optical modes, has the strongest intensity and its linewidth is 4.6 cm^–1. The infrared active lattice vibrations have been studied, eight optical modes were observed and assigned. The ultraviolet absorption edge is at 256 nm and the optical transparency range is up to 2500 nm at room temperature. The energy gap E_g of this crystal was obtained from the optical transmission spectra. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Absorption and emission of Ho3+ in germanate glasses

Absorption spectra of Ho³⁺ in germanate glasses were measured in the range 300–2500 nm and the intensity parameters were calculated by the Judd-Ofelt theory. Excitation and emission spectra were measured in the visible at a temperature range of 80–573 K. The radiative transition probabilities from the excited states [⁵F₄, ⁵S₂], ⁵F₅, ⁵I₄, ⁵I₅ and ⁵I₆, branching ratios and integrated emission cross-sections were calculated. The non-radiative relaxation rate from the (⁵F₄, ⁵S₂) levels is estimated to be about 2 × 10⁵ s^?1.     

X-ray Powder Diffraction Study and Vibrational Spectra of Calcium Cadmium Formate

It has been established that the double salt CaCd(HCOO)₄ is isostructural with CuSr(HCOO)₄. It crystallizes in the monoclinic space group P2/c - C2h⁴ with lattice parameters: a = 7.5309(2)Å, b = 8.8815(4)Å, c = 6.4267(2)Å, β = 92.153(2), and V = 429.55(3)ų. The analysis of the infrared spectra shows that the internal formate modes reflect the existence of two crystallographically inequivalent formate groups in the crystal lattices. The additional split of each formate mode into two components is due to the correlation field splitting. The frequency separations between the asymmetric and symmetric C-O stretching modes are explained in terms of different C-O bond lengths within each formate group and the frequency separation of the v₄ components in terms of different C-O bond lengths of the formate groups.     

Glass formation in and structural investigation of Li2S + GeS2 + GeO2 composition using Raman and IR spectroscopy

Li₂S + GeS₂ + GeO₂ ternary glasses have been prepared and a wide glass-forming range was obtained. The glass transition temperatures increase with the GeO₂ concentration in the glasses. The vibrational modes of both bridging (Ge–S–Ge) and non-bridging (Ge–S⁻) sulfurs are observed in Raman and IR spectra of binary Li₂S + GeS₂ glasses. Additions of GeO₂ to this binary glass increase the bridging oxygen band (Ge–O–Ge) at the expense of decreasing the bridging sulfur band (Ge–S–Ge), whereas the bands associated with the non-bridging sulfurs (Ge–S⁻) remain constant in intensity up to high GeO₂ concentrations. At higher concentrations of GeO₂ (⩾60%), the non-bridging oxygen band, which is not observed at low and intermediate GeO₂ concentrations, appears and grows stronger. From these observations, it is suggested that the added lithium ions favor the non-bridging sulfur sites over the oxygen sites to form non-bridging sulfurs, whereas the added oxygen prefers the higher field strength Ge⁴⁺ cation to form bridging Ge–O–Ge bonds. The structural groups in the Li₂S + GeS₂ + GeO₂ glasses that are consistent with results of Raman and IR spectra are described and are used to develop a structural model of these glasses.